Proper checking of enum with non zero default

proto2 syntax allows the first enum to have a non zero value. This means any
field using that default has a non zero default without having an explicit
default being set. So when deciding what runtime info is needed, don't rely
on an explicit default, always check that the values aren't zero.

Fixes https://github.com/google/protobuf/issues/1453

1 files changed, 5 insertions, 4 deletions

diff --git a/src/google/protobuf/compiler/objectivec/objectivec_helpers.cc b/src/google/protobuf/compiler/objectivec/objectivec_helpers.cc
index fda51807..196b39dd 100644
--- a/src/google/protobuf/compiler/objectivec/objectivec_helpers.cc
+++ b/src/google/protobuf/compiler/objectivec/objectivec_helpers.cc
@@ -757,10 +757,11 @@ bool HasNonZeroDefaultValue(const FieldDescriptor* field) {
     return false;
   }
 
-  if (!field->has_default_value()) {
-    // No custom default set in the proto file.
-    return false;
-  }
+  // As much as checking field->has_default_value() seems useful, it isn't
+  // because of enums. proto2 syntax allows the first item in an enum (the
+  // default) to be non zero. So checking field->has_default_value() would
+  // result in missing this non zero default.  See MessageWithOneBasedEnum in
+  // objectivec/Tests/unittest_objc.proto for a test Message to confirm this.
 
   // Some proto file set the default to the zero value, so make sure the value
   // isn't the zero case.